Hoist chain switch actuator



June 22, 1954 D. M. KING HOIST' CHAIN SWITCH ACTUATOR ZT wrA/ro' I $0044.) 019/5 A l #6 Filed Nov. 18, 1950 Patented June 22, 1954 UNITED STATES PATENT OFFICE Claims priority, application Great Britain November 23, 1949 2 Claims.

This invention relates to hoists, cranes or the like and has for its chief object to evolve means suitable for application to an electrically oper ated hoist, crane or the like and adapted to prevent overhoisting or overlowering.

According to the invention in a hoist, crane or the like wherein the driving motor is controlled by a switch, the actuation of which is effected through the medium of an arm or the like capable of angular movement, a resilient member is associated with the arm or the like in such a manner as to be disposed in the path of a striker element carried by the hoist rope, chain or the like, the arrangement being such that at a predetermined point in the travel of said rope, chain or the like the striker element will be caused to abut against the resilient member thereby to effect movement of the arm or the like and hence of the switch into its off position. Preferably the resilient member comprises a coil spring which is so dimensioned and arranged that the hoist rope, chain or the like will pass axially therethrough.

In order that the invention may be clearly understood and readily carried into effect the same will now be more fully described with reference to the accompanying drawings in which:

Figure l is a side elevational view showing a part of a chain hoist incorporating mechanism for preventing overhoisting.

Figure 2 is a section on the line 2-2 of Figure 1.

Figure 3 is a side elevational view of a detail.

Referring to the drawings I denotes a hoist chain which is attached at one end to a hoist block and is passed around a sprocket l I carried by said block, the free end of the chain carrying the usual load hook [2. In known manner the sprocket H is driven in one direction or the other to effect raising or lowering of the hook I2 by means of an electric motor (not shown) the operation of which latter is controlled by means of a switch housed within the casing designated I3. Constructional details of the switch contained within the casing l3 are generally known and one type of switch is known as a control circuit limit switch and is manufactured by the Igranic Electric Co. Ltd. of Bedford, England. The switch has an operating arm III associated therewith which is capable of a pivotal or angular movement to effect actuation of said switch. The arm I4 is a part of the switch constructed by the Igranic Electric Co. Ltd., and is provided with a spring for snapping it past a "dead centre to the off position of the switch when moved through a certain distance, and it is coupled by means of a link IE to one of a pair of operating levers l6 and I l which. latter are mounted for pivotal movement together about a pin 18 carried by the hoist block and are disposed in spaced parallel relationship so as to be at opposite sides of the hoist chain It. Pivotally mounted on a pin I9 supported by the levers I6 and I1 is a coiled spring 20 which is so disposed and of such diameter that the hoist chain It will pass freely therethrough. The diameter of the spring 20 is preferably so chosen as to be appreciably larger than that of the chain H1 in order to allow for swinging of said chain during operation of the hoist or for a permissible amount of deviation from the vertical due to sideways or lateral pulling of said chain.

Located at the lower end of the spring 20 is an annular member 2! which is adapted to form a suitable guide for the chain I0 and also to provide a convenient abutment surface. Mounted on the chain I0 at a point adjacent the hook I2 is a striker plate 22.

Preferably the coiled spring 20 is enclosed Within a sheath or cover of canvas, rubber or other suitable material as indicated at 23 in order to protect said spring from damage due to weather or other atmospheric conditions and also to provide for an improved appearance.

Finally the lever I1 is formed with a projection 24 adapted during normal operation of the hoist i. e. when the switch is in its on position and the levers are in the position shown in full lines in Figure 1, to abut against a stop 25 thereby to maintain said levers in the desired position.

When the hoist is operative and the switch is in its on position the mechanism above described will assume the positions shown in the full lines in Figure 1. On continued hoisting the striker plate 22 carried by the chain II] will eventually be caused to abut against the annular member 2| at the lower end of the spring 20 with the result that the latter will be compressed. The arrangement is such that a relatively slight compression of the spring 20 will cause an angular movement to be imparted to the operating levers l6 and I! such latter movement being effective to cause an appropriate angular movement of the arm I4 sufiicient to move the switch into the off position with resultant cutting out of the hoist motor. Further compression of the spring 20 will still be possible and that will allow for a reasonable amount of overrun should the brake normally fitted to the hoist not be properly adjusted and furthermore it will avoid the possibility of breakage of any part of the switch mechanism by overrunning caused either by maladjustment of the hoist brake or by variation in the operation of the latter due to varying loads on the hoist block.

In the preferred construction the arm 14 has a spring associated therewith which is adapted to urge said arm in the direction indicated by the arrow A on the drawing. The arrangement is such that on upward movement of the levers l6 and I! in the manner above described the link l5 and the arm It will be brought into a dead centre position wherein the three pivot points (i. e. the pivot point of the arm I4, the connection between the arm M and the link l5 and the connection between the link I5 and lever IE) are in a straight line whereupon the spring associated with said arm will become effective to force the latter to the limit of its movement corresponding to the oil? position of the switch. By virtue of this arrangement it will be appreciated that the degree of movement of the levers l6 and i7 necessary to effect actuation of the arm is relatively small. The resetting of the switch into the on position may readily be efiected by hand, an appropriate movement being imparted to the arm it or link Iii.

Furthermore, when the device above described is incorporated in a hoist including two or more falls of chain, it will be appreciated that the striker plate or the like will be disposed adjacent the load hook or bottom block.

I claim:

1. In apparatus of the class described having a driven shaft adapted to impart a raising and lowering motion to a hoist chain for controlling a switch the actuation of which latter is effected through the medium of an arm capable of angular or pivotal movement, the provision. of means for moving the switch automatically to its off position, such'mcans comprising lever means arranged to extend transversel with respect to the hoist chain and so mounted as to be capable of a pivotal movement, link mean connecting said lever means to the aforesaid actuating arm, a rigid stop adapted to co-operate with said lever means to maintain the same in a predetermined inoperative position, a coil spring supported for pivotal movement on said lever means, said coil spring being so dimensioned and arranged that the hoist chain will pass freely axially therethrough, and a striker element carried by said hoist chain and adapted at a predetermined point in the path of travel of the latter to abut against said coil spring thereby to impart an angular movement to said lever means sufiicient to effect movement of the actuating arm and hence of the switch to its off position.

2. In apparatus of the class described having a driven shaft adapted to impart a raising or lowering motion to a hoist chain for controlling a switch, the actuation of which latter is efiected through the medium of an arm capable of angular or pivotal movement, the provision of means for moving the switch automatically to its off position, such means comprising a pair of levers disposed in spaced parallel relationship at opposite sides of the hoist chain, said levers being capable of pivotal movement together about a common axis and one being operatively connected to the aforesaid actuating arm, a rigid stop with which the second lever is adapted normally to co-operate in such a manner as to maintain said levers in a predetermined inoperative position when said switch is in its on position, a coil spring supported for pivotal movement between said levers, said coil spring being so dimensioned and arranged that the hoist chain passes freely axially therethrough, and a striker element carried by said hoist chain and adapted at a predetermined point in the path of travel of the latter to abut against said coil spring thereby to impart an angular movement to said levers suificient to effect movement of the actuating arm and hence of the switch to its off position,

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,595,669 Kurner Aug. 10, 1926 2,274,175 Whitcomb Feb. 24, 1942 2,373,007 Baynes Apr, 3, 1945 2,428,578 Nelles Oct. '7, 1947 2,439,738 Hunter Apr. 13, 1948 

